1. Field of the Invention
The present invention relates to novel pharmaceutical compositions for the treatment of virus infections and cancer in mammals.
2. Description of the Related Art
Oligoadenylate synthetase (OAS) proteins are interferon-induced proteins characterized by their capacity to catalyze the synthesis of 2-prime, 5-prime oligomers of adenosine (2-5As). Hovanessian et al., EMBO 6:1273-1280 (1987) found that interferon-treated human cells contain several OASs corresponding to proteins of 40 (OAS1), 46 (OAS1), 69 (OAS2), and 100 (OAS3) kD. Marie et al., Biochem. Biophys. Res. Commun. 160:580-587 (1989) generated highly specific polyclonal antibodies against p69, the 69-kD OAS2. By screening an interferon-treated human cell expression library with the anti-p69 antibodies, Marie and Hovanessian, J. Biol. Chem. 267:9933-9939 (1992) isolated a partial OAS2 cDNA. They screened additional libraries with the partial cDNA and recovered cDNAs encoding two OAS2 isoforms. The smaller isoform is encoded by two mRNAs that differ in the length of the 3-prime untranslated region.
Northern blot analysis revealed that OAS2 is expressed as four interferon-induced mRNAs in human cells. The predicted OAS2 proteins have a common 683-amino acid sequence and different 3-prime termini. According to SDS-PAGE of in vitro transcription/translation products, two isoforms have molecular masses of 69 and 71 kD. Both isoforms exhibited OAS activity in vitro. Sequence analysis indicated that OAS2 contains two OAS1-homologous domains separated by a proline-rich putative linker region. The N- and C-terminal domains are 41% and 53% identical to OAS1, respectively. Likewise, OAS3 contains three tandem units of the OAS 1-homologous domains.
By fluorescence in situ hybridization and by inclusion within mapped clones, Hovanian et al., Genomics 52:267-277 (1998) determined that the OAS1, OAS2, and OAS3 genes are clustered with a 130-kb region on 12q24.2. 2-5As bind to and activate RNase I, which degrades viral and cellular RNAs, leading to inhibition of cellular protein synthesis and impairment of viral replication.
A fourth human OAS gene, referred to as OASL, differs from OAS1, OAS2 and OAS3 in that OASL lacks enzyme activity. The OASL gene encodes a two-domain protein composed of an OAS unit fused to a 164 amino acid C-terminal domain that is homologous to a tandem repeat of ubiquitin. (Eskildsen et al., Nuc. Acids Res. 31:3166-3173, 2003; Kakuta et al., J. Interferon & Cytokine Res. 22:981-993, 2002.)
The present invention fulfills needs in the art by providing engineering and modification of oligoadenylate synthetase proteins to improve their drug properties.